Overwrite existing buildings, changes/additions.

[kahlzun]

Hi there! I am looking to 'tweak' a few parts of my existing game, and was wondering if I can do this with a mod, or whether I would need to directly edit the xml files in Core?

Specifically, the Vents are not transporting heat/cold effectively enough, and i'm seeking to beef them up a bit.

[1000101]

Just create your own mod directory with the same structure as core for the files you need (not the whole thing).

Copy the file you want to mod to your mod directory (ie, /Mods/Core/Defs/ThingDefs/blah.xml to /Mods/MyMod/Defs/ThingDefs/blah.xml)

Then made the changes to your mods file.

Also, make sure you enable your mod.

[kaptain_kavern]

Think of it like that :
If something is already defined (in vanilla or a previously charged mod)  and your mod (or another) define it again, it'll overwrite.
That's why mod order sometimes matters. And why modpacks are provided with config file including already sorted mod order list. And again why some mods are incompatible (say Mod A overwrite values that Mod B need to be vanilla, etc)